The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Typical acoustic guitars have a neck attached to one end of a hollow wooden body. Nylon or steel strings are strung under tension between the top of the neck and an opposite end of the body. The strings gradually range from thick bass strings toward the bottom of the guitar to thin treble strings toward the top of the guitar on a right-handed guitar, opposite on a left-handed guitar. String tension may be dependent upon string material and mass. The body is comprised of a front soundboard connected to a backboard by a curved side wall. The soundboard is generally pierced by a sound hole that is traditionally centered, but known guitar embodiments may include sound holes disposed anywhere on the soundboard. The soundboard is made relatively thin to vibrate in response to the vibrations of the strings to amplify the sound.
The soundboard is typically reinforced by internal braces attached to its internal guitar body including internal sides to provide structural reinforcement and dimensional stability under the tension of the strings. Although the braces must be stiff enough to provide support, they must still allow the soundboard to vibrate. The most common braces are each attached to the soundboard along its entire length, particularly to thin soundboards. Typical known bracing includes composite materials, wood or synthetic materials that are larger in cross section or more in number as the soundboard is thinned to make up for structural integrity lost due to thinning of soundboard. Known soundboard embodiment are built with either auxiliary bracing attached by glue or other means directly to the soundboard itself or by use of alternate soundboard material construction using composites, honeycomb reinforcement, laminated construction or extra thick wooden soundboards to prevent failure of the soundboard by countering the physical forces introduced by attached strings. Forces acting upon the soundboard by attached strings include tension, compression, shear and moment.
Moment forces, particularly, require stronger bracing, having greater mass than otherwise would be required if compression, shear and tension forces would be the only forces required to brace. Therefore, it would be advantageous to construct a stringed instrument that decreases moment forces acting upon the guitar soundboard, thereby decreasing tone dampening and undesirable harmonic distortion effects, and increasing volume output.
During the life of an instrument, environmental conditions such as humidity changes can cause dimensional changes in wooden bracing, the soundboard and/or the instrument as a whole. Additionally, changes in a weight or radius of instrument strings can affect position of the strings over the neck and therefore “playability.” For example, higher tension strings will result in the bridge and saddle rotating forward—lowering the effective height of the strings over the neck and directly affecting the overall string length thus affecting instrument playability and tune. Reducing tension of a traditional truss rod within the neck to compensate for the rotation of the bridge in order to raise the strings to the correct height above the fingerboard surface under such condition can result in a reduction to overall string length due to increased neck bow requiring lowering of the string tension to correct the open string note. The change in “scale length” i.e., a distance between saddle and nut, will cause a change in the non-adjustable fretted strings to saddle lengths causing and compounding intonation issues.
Therefore, to maintain a preferably or consistent sound output, adjustment to the soundboard height via adjustment of an underside height adjuster assembly and an assembly to control bridge rotation is desirable. An assembly configured to adjust string height over the fingerboard and control bridge rotation between the bridge saddle and neck nut enables a user to control “action” or instrument “playability,” and precision control over production of a desired note. These controls in combination with the traditional truss rod adjustment offer more parametric parameters of control over the instrument itself than would otherwise be afforded to the musician and his individual preferences while allowing faithful sound production.
Further, in guitar and string instrument production, initial string height over the fingerboard and proper angle of strings is achieved through a laborious process of fitting the neck to the body at a correct angle to the installed bridge so that string alignment and string height over the fingerboard are within specification. Fitting typically includes removing, i.e., carving, wood from the neck heel and mating surface to achieve the correct angle and height of the neck relative to the bridge or saddle. In some guitar embodiment, shims are placed between the neck-body interface and the neck heel-body in order to achieve the proper angle and height. Proper neck angle often takes a many iterations of fitting to achieve the desired results and can be labor intensive.
Therefore, it would be advantageous to set the neck angle and bridge close to desirable settings prior to installing strings. Subsequent to string installation, the initial settings may then be adjusted without a neck reset or other laborious process such as de-stringing and resetting the necks shims, thereby increasing production efficiency and more advantageously accommodating differences in soundboard wood properties.